Such heat exchangers, as is well known, are used especially in motor vehicles having internal combustion engines, so as to constitute either an engine cooling radiator or a cabin heating radiator. In either of these two applications, an engine coolant fluid, which is usually water with the addition of a suitable antifreeze preparation, flows through the tubes in the bundle, while a stream of air flows over the tubes in the bundle. In this familiar type of heat exchanger, it is usual to provide the same number of holes in the header plate as there are tubes in the bundle, so that each tube end is received individually in a respective hole in the header plate, to which it is sealingly secured.
In French patent application No. 91 03411 in the name of the present Applicant, a heat exchanger is proposed which is of the type comprising a bundle of parallel tubes and a header plate having holes, each of which receives the respective ends of a plurality of adjacent tubes which are part of a common group of tubes. A compressible sealing gasket is generally interposed between the edge of the hole and the tube ends in that group. Due to the fact that the respective ends of the tubes in a group are received in a single hole in the header plate, instead of each one being received individually in a separate hole of the plate, the pitch of the tubes is able to be reduced to a minimum value. In this way the thermal performance of the heat exchanger can be optimised while the dimensions of the header plate are minimised.
However, in the heat exchanger of the type just mentioned, the tubes of any one of the said groups are part of different rows of tubes in the bundle. In addition, this heat exchanger is most particularly suitable where there are two rows of tubes in the bundle, that is to say the latter is a twin-row bundle.